Synergistic effect of lanthanum oxide on intumescent flame-retardant polypropylene-based formulations

Synergistic effects of lanthanum oxide (La2O3) on the flammability and thermal properties of intumescent flame-retardant polypropylene (IFR-PP) composites are investigated in the study. The limiting oxygen index (LOI), UL-94 test, and cone calorimeter results show that the flame retardancy of IFR-PP is improved significantly by the introduction of La2O3. The results of thermogravimetric analysis (TGA) indicate that thermal stability of IFR-PP is also enhanced. SEM pictures reveal that La2O3 addition improve the formation of a homogenous and compact intumescent char layer on the surface of the composites. The possible mechanism of the synergistic effects between La2O3 and IFR is proposed in the paper.